DUST REMOVING APPARATUS

Abstract: An object of the present invention is to improve the soot and dust collection efficiency by preventing the leakage of a dusty gas even when a high-temperature dusty gas is removed. The present invention relates to a dust removing apparatus in which a filter element (11) is held on a filter element mounting frame (12), characterized in that a flange (11a) is provided at the end portion of the filter element (11) which is on the side of a dusty gas (21) so that the portion of the flange (11a) which is on the side of a clean gas (22) is pressed against the portion of a flange (12a) of the filter mounting frame (12) which is on the side of the dusty gas via a packing (15) to prevent the leakage of the dusty gas (21). A plurality of honeycomb type filter elements of the above-described construction are put together and housed in a frame to form a honeycomb pack.

Description: TECHNICAL FIELD The present invention relates to a dust removing apparatus of combustion gas, coal gas and the like. BACKGROUND TECHNIQUE Fig. 11 schematically illustrates a filter element used heretofore as a dust removing apparatus of combustion gas and gas produced by gasifying petrified fuel such as coal. Referring to Fig. 11, a prior art is described by taking the removal of soot dust contained in combustion exhaust gas as an example. In Fig. 11, a pillar-shaped filter element 011 having a substantially square section is accommodated in a filter element mounting frame 012 made of metal or ceramics and both ends of the elements are held by metal fittings 013. Further, filling material 014 such as felt is filled into a gap between the filter element 011 and the frame 012 to seal therebetween. Dirty gas 21 containing soot dust in combustion exhaust gas is passed through the filter element 011 to be filtered therein, so that soot dust in the exhaust gas is removed and purified gas 22 is discharged. As shown in Fig. 13, a plurality of the filter elements are collected and are accommodated into an outer frame 023 to be used as a pack. Further, Fig. 14 illustrates a conventional dust removing apparatus using a honeycomb pack in which a unit number of honeycomb type filter elements are collected to form a unit lot. The apparatus includes thin paper-like seal packings 02 disposed on the side of dirty gas and on the side of purified gas of filter elements 01 to hold the seal packings 02 between contact surfaces of the filter elements 01. The seal packings 02 are wound on all of the filter elements 01 arranged into a plurality of row and columns and all of the filter elements are finally fastened by a honeycomb pack frame externally. As shown in Fig. 15, the whole outer periphery of the filter elements 01 is wound at inlet and outlet sides thereof by seal packings 04 and is fastened by the honeycomb pack frame 03 to effect sealing in the honeycomb pack frame 03. Fig. 16 schematically illustrates an order of assembling such a honeycomb pack. More particularly, first of all, as shown in Fig. 16(A), a honeycomb pack bottom frame 05 and a center partition plate 06 are held by a jig 09. Then, as shown in Fig. 16(B), the filter elements 01 each having the above paper-like seal packings 02 which are previously wound on both ends of the filter element are piled up. In this case, seal packings 04 are disposed on outer end portions of the bottom partition plate 05 and the center partition plate 06. After the filter elements have been piled up completely, seal packings 04 are attached on the whole outer peripheries of the piled filter elements as shown in Fig. 16(C). Then, as shown in Fig. 16(D), an upstream lattice frame 07 is fitted onto the pack on the dirty gas side thereof and a downstream lattice frame 08 is fitted onto the pack on the purified gas side thereof. Finally, as shown in Fig. 16(E), the pack frame 03 disposed on the upper surface is fastened to complete the pack. In the dust removing apparatus fabricated by the above-described processes, the dimensional accuracy of the filter element is varied and accordingly adjustment of clearance is performed by the piling method of the packings. Thus, the sealing performance is influenced by the technical skill of operators who perform the assembling of the pack as described above. In the conventional filter element shown in Fig. 11, when the temperature of the dirty gas containing the soot dust is high, a difference between the filter element 011 and the filter element mounting frame 012 in which the filter element is accommodated is increased due to the high temperature. The increased difference cannot be covered by the resilient width of the filling material 014 such as felt filled therebetween to thereby form the clearance. Accordingly, as shown by arrow a of Fig. 12, gas is leaked through the clearance and part of soot dust cannot be filtered by the filter element 011 to thereby reduce the soot dust collection factor. For example, when the filter element 011 is formed into a square pillar having one side of 200 mm and a temperature of the dirty gas 21 is 800 °C on condition that the filter element 011 is made of ceramics and has the coefficient of thermal expansion of 1×10 -6 /°C and the filter element mounting frame 012 is made of metal and has the coefficient of thermal expansion of 18×10 -6 /°C, an increase ΔHc1 of the clearance between the filter element 011 and the filter element mounting frame 012 in the gas flowing direction upon the normal assembling (20 °C) and the high-temperature operation is given by Δ Hc1 = 200×(18-1)×10 -6 ×(800-20) = 2.652 mm Further, in the conventional dust removing apparatus shown in Fig. 14, the seal packings are wound on the gas inlet side surfaces and the gas outlet side surfaces of the filter elements, and the filter elements are piled up vertically and horizontally. In addition, the packings are provided under the honeycomb pack frame and the frame is fastened to effect sealing completely. Accordingly, the assembling of the apparatus is apt to be affected by the operator's assembling ability. Error in the element dimension and a problem of the extension difference at the high temperature occur. In other words, since the honeycomb pack frame made of metal expands more as compared with the element made of ceramics, occurrence of looseness is unavoidable even if the pack is sufficiently fastened. Further, in the case of the class of 1,000 mm H 2 O in which a differential pressure between the inlet side and the outlet side of gas is very large, there occurs a phenomenon that the seal packing on the inlet side is shifted inside gradually. Accordingly, the sealing of the honeycomb pack of the dust removing apparatus has a problem and its improvement is pressing. To prevent the increasing of pressure loss, it is known from JP-A-2-75315 & Patent Abstracts of Japan 121C725 to provide an inwardly facing flange around the inner periphery of a casing and employing a bottomed cylindrical filter element having an outwardly facing flange around the outer periphery thereof. An additional seal packing may be disposed between the flanges. During filtering, particles present in the gas are trapped by the filter element for gas purification. A similar dust removing apparatus comprising a honeycomb pack in which a plurality of filter elements is collected and accommodated to form a unit lot and dirty gas is converted into purified gas by said filter elements mounted through a flange-shaped protrusion at their inlet sides to a filter element mounting frame which is mounted to a honeycomb pack frame body, is described in EP-A-0 410 200. The filter elements are made of permeable porous sintered metal particles to avoid the shock-sensitivity ceramic filter elements. The problems of the conventional sealing of honeycomb pack are overcome in the dust removing apparatus defined in the appended claims as follows. (1) By performing sealing between the flange on the dirty gas side of the filter element and the flange on the dirty gas side of the filter element mounting flange, pressure of the dirty gas is utilized to compress the seal packing and improve the sealing characteristic. Further, since sealing is performed between the filter element on the dirty gas side and the flange of the filter element mounting frame, the sealing performance is not reduced by the extension difference of the filter element and the filter element mounting frame under high temperature. (2) Even if force in the opposite direction to that in the normal dust removing operation acts on the filter element upon the dust removing operation in the revers direction, the filter element is held exactly by the preferable pressing bolt of the mounting metal fitting of the filter element mounting frame and shock is not given to the filter element. Further, the filter element can be held by the preferable holding piece of the filter element and the cotton-like ceramic fiber exactly without occurrence of vibration to prevent damage of the filter element. (3) The honeycomb pack frame body is mounted to the pack mounting frame of the gas duct through the seal packing, so that the sealing performance can be improved. (4) Since influence due to the ability of the assembling operator is not affected as in the conventional honeycomb pack, not only the sealing performance but also the reliability of the whole honeycomb pack can be improved. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating a structure of a flanged ceramic filter element mounted to a separate filter housing; Fig. 2 is a diagram illustrating the filter element of Fig. 1 in a high temperature state; Fig. 3 is a graph showing a relation of a gas leakage factor and a differential pressure before and behind a filter of the filter element of Fig. 1 and the prior art; Fig. 4 is a sectional view of a honeycomb filter element of the present invention with the filter element being mounted; Fig. 5 is a perspective view of the honeycomb filter element of Fig. 4; Fig. 6 is a front view of a honeycomb pack of 20 honeycomb filter elements of Fig. 5; Fig. 7 is a sectional view taken along line B-B of Fig 6; Fig. 8 is a sectional view taken along line C-C of Fig. 6; Fig. 9 is a perspective view showing a mounted honeycomb pack; Fig. 10(a) is a schematic diagram illustrating an examination apparatus of the sealing characteristics of the packing of a filter element; Fig. 10(b) is a diagram for explaining a heat cycle in the examination; Fig. 10(c) is a graph showing an examination result; Fig. 11 is a schematic diagram illustrating a filter element of a conventional dust removing apparatus; Fig. 12 is a schematic diagram illustrating the conventional dust removing apparatus in a high temperature state; Fig. 13 is a perspective view showing the conventional filter element being packed; Fig. 14 is a schematic diagram illustrating a seal structure of a conventional honeycomb filter element; Fig. 15 is a schematic diagram illustrating a seal structure between a conventional honeycomb pack frame and the honeycomb filter element; and Fig. 16(A) to (E) schematically illustrate assembling processes of a conventional honeycomb pack. In Figs. 1 and 2 numeral 11 denotes a pillar-shaped filter element having a square section which does not form part of the claimed invention. The filter element 11 is made of porous material such as ceramics. Disposed at an end on the side of dirty gas 21 of the filter element 11 is a seal flange 11a which is protruded in the direction perpendicular to an axis of the filter element 11. Numeral 12 denotes a filter element mounting frame for accommodating the filter element 11 movably in the gas flowing direction. A seal flange 12a for forming a recess corresponding to the seal flange 11a of the filter element 11 is formed at an end on the side of dirty gas 21 of the mounting frame 12, positioned on the side of purified gas 22 with respect to the seal flange 11a of the filter element 11. The seal flange 11a of the filter element 11 is disposed between the seal flange 12a and a metal fitting 13 attached on an end on the side of dirty gas 21 of the seal flange 12a. Further, a seal packing 15 made of ceramics fiber is held between the seal flanges 11a and 12a. In the filter element structured above, the seal flange 11a of the filter element 11 is pressed on the seal flange 12a of the filter element mounting frame 12 by pressure of dirty gas 21 containing soot dust flowing in the arrow direction to clinch the seal packing 15 therebetween, so that the sealing characteristic is satisfactory and leakage of dirty gas 21 containing soot dust is prevented. Accordingly, even when the temperature of the dirty gas 21 is increased to produce a thermal extension difference between the filter element 11 and the filter element mounting frame 12, the seal flange 11a of the filter element 11 is always pressed on the seal flange 12a of the filter element mounting frame 12 through the seal packing 15. Accordingly, the sealing characteristic for the dirty gas 21 can be ensured and the soot dust collection factor by the filter element 11 can be improved remarkably. For example, as shown in Fig. 1, when a distance x between opposite surfaces of the flange 12a of the filter element mounting frame 12 and the metal fitting 13 is 20 mm and the temperature of the dirty gas 21 is as higher as 800 °C on condition that the filter element mounting frame 12 is made of metal and has the coefficient of thermal expansion of 18×10 -6 /°C and the filter element 11 is made of ceramics and has the coefficient of thermal expansion of 1×10 -6 /°C, the increase ΔHc1 of the clearance produced by the thermal extension difference between the flanges 11a and 12a is given in the same manner as described in the "BACKGROUND TECHNIQUE" by Δ Hc1 = 20×(18-1)×10 -6 ×(800-20) = 0.2652 mm However, even when the clearance is increased, the seal flange 11a is always pressed on the seal flange 12a through the seal packing 15 by the pressure of the dirty gas 21 and accordingly leakage of the dirty gas 21 does not occur. Fig. 3 shows a relation between an input-output differential pressure and a leakage ratio of the filter element 11. In Fig. 3, the characteristic of the apparatus of the present invention is represented by line 1 and the conventional characteristics of the apparatus shown in Figs. 11 and 12 are represented by lines 2 and 3. The line 3 represents the characteristic at the temperature of the dirty gas of 500 °C in the prior art and the leakage ratio thereof is not very large, while when the temperature of the exhaust gas is increased to 800 °C, the leakage ratio is increased several times as shown by the line 2. Even when the temperature of the dirty gas becomes 800 °C, the leakage ratio can be suppressed to the same degree or less as in the prior art as shown by the line 1. Further, as shown in Fig. 3, in the present invention, even if the temperature of the dirty gas is high, the leakage ratio of the dirty gas in the differential pressure of about 1000 mm H 2 O can be suppressed to about 0.5 %. Consequently, when the dirty gas having the concentration of soot dust at the inlet of 10 g/Nm 3 is subjected to the dust removing process, the concentration of soot dust at the outlet is about several hundreds mg/Nm 3 in the conventional dust removing apparatus, whereas in the present invention the concentration of soot dust at the outlet can be reduced to about several tens mg/Nm 3 . Referring now to Figs. 4 to 9, an embodiment of the present invention is described. As shown in Figs. 6 to 8, the embodiment includes a honeycomb pack 101 having a substantially square section and formed by 20 horizontally disposed honeycomb type filter elements 102 collected to be accommodated to form a unit lot. The honeycomb pack 101 includes, as shown in Figs. 6 and 7, square pack frame bodies 101a, 101a having an L-shaped section and disposed at both sides thereof. A plurality of filter element mounting frames 103 previously mounted to the pack frame body 101a, 101a and horizontally disposed are arranged into a lattice and the filter elements 102 are mounted in the filter element mounting frame 103. As shown in Figs. 4 and 5, the honeycomb filter element 102 includes a seal flange 112 disposed at an end on the side of dirty gas 21 to be protruded therefrom. The filter element 102 includes a plurality of plate-like porous ceramic bodies 102a disposed to cross each other horizontally and vertically so `that the filter element is divided into a plurality of honeycomb gas passages horizontally and vertically, and closed portions are disposed alternately at one ends and the other ends of the gas passages as shown by hatched portions of Fig. 5. Accordingly, dirty gas 21 coming into the passages from one open end as shown by arrow of Fig. 5 is filtered by the porous ceramic bodies 102a and then come into adjacent gas passages to be converted into purified gas, so that the purified gas 22 is discharged from the other open ends. A support and sealing structure between the individual accommodated honeycomb filter element 102 and the filter element mounting frame 103 is now described. As shown in Fig. 4, a seal flange 111 is disposed in correspondence manner to the seal flange 112 disposed in the inlet side of dirty gas 21 of the filter element 102 so that the seal flange 111 is in contact with the downstream side (purified gas side 22) of the flange 112 at the inlet side of the dirty gas 21 of the filter element mounting frame 103. The filter element 102 is mounted in the filter element mounting frame 103 movably in the axial direction of the filter element 102 and a seal packing 105 is interposed therebetween. Further, mounting metal fittings 107 are disposed before and behind the filter element 102, that is, at the inlet side of dirty gas 21 and the outlet side of purified gas 22 in the filter element mounting frame 103 and are mounted by means of fixing bolts 113. The mounting metal fitting 107 disposed at the side of dirty gas 21 is provided with a pressing bolt 108 for pressing the seal flange 112 of the filter element 102 not to be shaky, and a holding piece 116 is disposed between the filter element 102 and the filter element mounting frame 103 near the purified gas outlet to hold the filter element 102 horizontally. In addition, a gap between the filter element 102 and the filter element mounting frame 103 is filled with cotton-like ceramic fiber 106. A sealing and mounting structure of the honeycomb pack 101 including all of the 20 filter elements 102 mounted as described above is now described. As shown in Fig. 9, a plurality of honeycomb packs 101 are disposed on both sides of a dirty gas duct 115 disposed in the vertical direction of a center portion to be opposite to each other. A pack mounting metal fitting 104 is disposed on the dirty gas inlet side around the frame body 101a of the honeycomb pack 101 being in contact with the dirty gas duct 115 and a seal packing 117 is held between a mounting flange 115a of the dirty gas duct 115 and the honeycomb pack 101 and is fastened by bolts 110 and nuts (refer to Fig. 8). In Fig. 9, numeral 114 denotes a scramble dirty gas duct for supplying the dirty gas 21 to the dirty gas duct 115 from the upper portion and numeral 114a denotes a scramble dirty gas duct for discharging the dirty gas 21 from the dirty gas duct 115 to the lower portion. In the embodiment structured above, as shown by arrow of Fig. 9, the dirty gas 21 coming from the scramble dirty gas duct 114 into the dirty gas duct 115 enters the passages of the filter elements 102 of the honeycomb pack 101 and is filtered upon passing through the porous ceramic bodies 102a of the filter elements 102 to become the purified gas 22. The purified gas 22 comes into the passages of the adjacent filter elements 102 and is taken out from the honeycomb pack 101. At this time, since the seal flanges 112 are disposed on the side of the dirty gas 21 of the filter elements 102, the filter elements 102 are subjected to a greater pressure differential as compared with the prior art so that the packings 105 are compressed and pressed against the flanges 112 to improve the sealing characteristic. Accordingly, the sealing characteristic can be improved remarkably as compared with the conventional concentric seal in the flowing direction of gas shown in Figs. 14 and 15. More particularly, since the conventional seal is dependent on the fastening force upon collection of the pack and has no force except the fastening force, the conventional seal is loosened due to the extension difference during operation. Accordingly, when a differential pressure is applied, there is a vicious circle that the seal packing is gradually shifted to the center side and hence the hoops of the pack are further loosened. On the contrary, in the embodiment, the differential pressure due to the dirty gas can be utilized to improvement of the sealing characteristic as described above. Further, since the seal flange 112 on the side of dirty gas of the filter element 102 is held through the seal packing 105 by the filter element mounting frame 103, looseness and reduction of the sealing performance do not occur even if the extension difference due to the temperature occurs between the filter element 102 and the filter element mounting frame 103. Fig. 10 shows an examination apparatus of the sealing characteristic of the packing and an examination result thereof. As shown in Fig. 10(a), the examination apparatus used a metal element 102t having the same shape as that of the filter element 102 instead of the filter element 102 and the metal element 102t was accommodated in a pack 103t corresponding to the filter element mounting frame 103. Thus, an amount of leakage from a seal packing 105t (the seal packing 105 of the embodiment) using ceramic fiber 106t was measured while differential pressure ΔP is varied. An amount of gas leakage of the conventional system shown in Figs. 14 and 15 indicated a relatively large value of 2 to 3 %. The examination of the embodiment used the metal element 102t including a flange 112t corresponding to the seal flange 112 and examined the leakage amount in the seal packing 105t for two cases before and after a heat cycle as shown in Fig. 10(c). The heat cycle shown in Fig. 10(b) was adopted. As a result, as shown in Fig. 10(c), it has been confirmed that the leakage amount is about 0.3 % in the actually occurring differential pressure of 1000 to 1200 mm H 2 O of the dust removing apparatus and the leakage amount in the seal packing 105t is reduced greatly. Further, in the embodiment, in order to reinforce and offset the above sealing performance, since the mounting metal fitting 107 is disposed on the inlet side of dirty gas and on the outlet side of purified gas of the filter element 102 to press the filter element 102 thereon and the pressing bolt 108 is provided in the mounting metal fitting 107 on the inlet side of dirty gas to press the seal flange 112 of the filter element 102, looseness in the high temperature can be prevented and the filter element 102 can be exactly held against the differential pressure in the opposite direction upon the dust removing operation in the reverse direction. Further, by providing the holding piece on the outlet side of purified gas, it can be prevented that the horizontal degree of the filter element 102 is varied to damage a root portion of the seal flange. In addition, since the space between the filter element mounting frame 103 and the filter element 102 is filled with the cottonlike ceramic fiber 106, vibration upon the dust removing operation in the reverse direction can be relieved. Furthermore, in the embodiment, since the pack mounting frame 104 of the frame body 101a of the honeycomb pack 101 is fixedly mounted to the mounting flange 115a of the opposite dirty gas duct 115 through the seal packing 117 by fastening the nuts to the bolts 110, the honeycomb pack can be mounted exactly in the improved state of the sealing characteristic. In the embodiment, the plurality of honeycomb packs 101 are disposed opposite to each other on both the sides of the dirty gas duct 115, while a single honeycomb pack can be disposed on each side of the dirty gas duct 115 to be opposed to each other. Alternatively, a single or a plurality of honeycomb packs can be disposed on only one side of the dirty gas duct 115. Further, in the embodiment, the honeycomb pack 101 is mounted to the dirty gas duct 115 to hold the seal packing 117 therebetween, while the honeycomb pack 101 can be mounted to a duct on the side of purified gas through the seal packing. INDUSTRIAL AVAILABILITY As described above, in the dust removing apparatus according to the present invention, the flange is disposed on the dirty gas side of the filter element, and the purified gas side of the flange and the dirty gas side of the flange of the filter element mounting frame positioned on the purified gas side with respect to the flange are disposed in opposing relationship to each other to hold the filter element in the filter element mounting frame, so that the purified gas side of the flange of the filter element is always pressed to the dirty gas side of the flange of the filter element mounting frame even if there is a thermal extension difference between the filter element and the filter element mounting frame. Since the leakage of dirty gas can be prevented exactly and the collection factor of soot dust can be improved, the dust removing apparatus can be utilized industrially widely. Further, the plurality of honeycomb filter elements of porous ceramic substance are collected and accommodated to form a unit lot and the seal packing is held between the purified gas side of the flange disposed on the dirty gas side of the filter element and the dirty gas side of the flange of the filter element mounting frame mounted to the honeycomb pack frame body to hold the filter element to thereby realize the stable seal. In addition, the flange on the dirty gas side of the filter element is pressed to the flange of the filter element mounting frame through the packing by the pressure of the dirty gas, which is utilized as the pressing force to the packing and the filter element mounting frame, to thereby attain the sealing operation exactly. Furthermore, since the flange on the dirty gas side of the filter element is held by the flange of the filter element mounting frame, looseness and reduction of the sealing performance do not occur even if there is the extension difference due to the high temperature between metal and the filter element of ceramic substance, so that the collection factor of soot dust is improved and the dust removing apparatus is useful industrially.

Claims: A dust removing apparatus comprising a honeycomb pack (101) in which a plurality of filter elements (102) is collected and accommodated to form a unit lot and dirty gas (21) is converted into purified gas (22) by said filter elements (102) mounted to a filter element mounting frame (103) which is mounted to a honeycomb pack frame body (101a), each of said filter elements (102) having disposed a flange (112) on the dirty gas inlet characterized in that said filter elements (102) are made of porous ceramic substance of honeycomb structure and a seal packing (105) is held between the purified gas side of said flange (112) and the dirty gas side of a flange (111) of said filter element mounting frame (103) to hold said filter element (102), the two flanges (112) and (111) being disposed opposite to each other. A dust removing apparatus according to claim 1, comprising mounting metal fittings (107) disposed on both the dirty gas inlet side and the purified gas outlet side of said filter element (102) in said filter element mounting frame (103), said mounting metal fitting (107) on the dirty gas inlet side including a pressing bolt (108) for pressing said flange (112) of said filter element (102), a holding piece (116) of said filter element (102) disposed between said filter element (102) near the purified gas outlet and said filter element mounting frame (103), and cotton-like ceramic fiber (106) for filling a space between said filter element mounting frame (103) and said filter element (102). A dust removing apparatus according to claim 1 or 2, comprising pack mounting metal fittings (104) disposed on both the dirty gas side and the purified gas side of said honeycomb pack frame body (101a), one of said pack mounting metal fitting (104) fixedly mounted to a pack mounting frame of a gas duct (115) to hold a seal packing (117) therebetween.

Inventors: AKITU YASUO, FUJINO TETSUYA, HORI YOSIAKI, KITAGAWA YUICHIRO, NAGASHIMA KIYOSHI, UCHIDA SATOSHI, UEDA TETSUYA, URAKATA HISATAKA, AKITU, YASUO, FUJINO, TETSUYA, HORI, YOSIAKI, KITAGAWA, YUICHIRO, NAGASHIMA, KIYOSHI, UCHIDA, SATOSHI, UEDA, TETSUYA, URAKATA, HISATAKA, AKITU, YASUO 24-1, AOYAMA-CHO 1-CHOME, FUJINO, Tetsuya, Nagasaki Ship.&amp; Mach.Works, HORI, YOSIAKI NGK TAKEMI-RYO, KITAGAWA, Yuichiro, Nagasaki Ship.&amp; Mach.Works, NAGASHIMA, Kiyoshi, Nagasaki Ship. &amp; Mach.Works, UCHIDA, SATOSHI MITS. JUKOGYO KABUSHIKI KAISHI, UEDA, Tetsuya, Nagasaki Ship. &amp; Mach. Works, URAKATA, Hisataka, Nagasaki Ship.&amp; Mach.Works
Applicants: MITSUBISHI HEAVY IND LTD, NGK INSULATORS LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA, NGK INSULATORS, LTD.
Application year: 1994
Main classification: B01D46
IPC codes: B01D46